Commit 0c4b0f81 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'mips_4.19_2' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux 

Pull MIPS fixes from Paul Burton:

  - Fix microMIPS build failures by adding a .insn directive to the
    barrier_before_unreachable() asm statement in order to convince the
    toolchain that the asm statement is a valid branch target rather
    than a bogus attempt to switch ISA.

  - Clean up our declarations of TLB functions that we overwrite with
    generated code in order to prevent the compiler making assumptions
    about alignment that cause microMIPS kernels built with GCC 7 &
    above to die early during boot.

  - Fix up a regression for MIPS32 kernels which slipped into the main
    MIPS pull for 4.19, causing CONFIG_32BIT=y kernels to contain
    inappropriate MIPS64 instructions.

  - Extend our existing workaround for MIPSr6 builds that end up using
    the __multi3 intrinsic to GCC 7 & below, rather than just GCC 7.

* tag 'mips_4.19_2' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
  MIPS: lib: Provide MIPS64r6 __multi3() for GCC < 7
  MIPS: Workaround GCC __builtin_unreachable reordering bug
  compiler.h: Allow arch-specific asm/compiler.h
  MIPS: Avoid move psuedo-instruction whilst using MIPS_ISA_LEVEL
  MIPS: Consistently declare TLB functions
  MIPS: Export tlbmiss_handler_setup_pgd near its definition
parents 2ab054fd 690d9163

arch/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -841,6 +841,14 @@ config REFCOUNT_FULL 
	  against various use-after-free conditions that can be used in

	  security flaw exploits.



config HAVE_ARCH_COMPILER_H

	bool

	help

	  An architecture can select this if it provides an

	  asm/compiler.h header that should be included after

	  linux/compiler-*.h in order to override macro definitions that those

	  headers generally provide.



config HAVE_ARCH_PREL32_RELOCATIONS

	bool

	help

arch/mips/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ config MIPS 
	select GENERIC_SMP_IDLE_THREAD

	select GENERIC_TIME_VSYSCALL

	select HANDLE_DOMAIN_IRQ

	select HAVE_ARCH_COMPILER_H

	select HAVE_ARCH_JUMP_LABEL

	select HAVE_ARCH_KGDB

	select HAVE_ARCH_MMAP_RND_BITS if MMU

arch/mips/include/asm/asm-prototypes.h

+1 −0
Original line number Diff line number Diff line
@@ -5,3 +5,4 @@ 
#include <asm-generic/asm-prototypes.h>

#include <linux/uaccess.h>

#include <asm/ftrace.h>

#include <asm/mmu_context.h>

arch/mips/include/asm/atomic.h

+3 −1
Original line number Diff line number Diff line
@@ -122,8 +122,8 @@ static __inline__ int atomic_fetch_##op##_relaxed(int i, atomic_t * v) \ 
		"	" #asm_op " %0, %1, %3				\n"   \

		"	sc	%0, %2					\n"   \

		"\t" __scbeqz "	%0, 1b					\n"   \

		"	move	%0, %1					\n"   \

		"	.set	mips0					\n"   \

		"	move	%0, %1					\n"   \

		: "=&r" (result), "=&r" (temp),				      \

		  "+" GCC_OFF_SMALL_ASM() (v->counter)			      \

		: "Ir" (i));						      \
@@ -190,9 +190,11 @@ static __inline__ int atomic_sub_if_positive(int i, atomic_t * v) 
		__asm__ __volatile__(

		"	.set	"MIPS_ISA_LEVEL"			\n"

		"1:	ll	%1, %2		# atomic_sub_if_positive\n"

		"	.set	mips0					\n"

		"	subu	%0, %1, %3				\n"

		"	move	%1, %0					\n"

		"	bltz	%0, 1f					\n"

		"	.set	"MIPS_ISA_LEVEL"			\n"

		"	sc	%1, %2					\n"

		"\t" __scbeqz "	%1, 1b					\n"

		"1:							\n"

arch/mips/include/asm/compiler.h

+35 −0
Original line number Diff line number Diff line
@@ -8,6 +8,41 @@ 
#ifndef _ASM_COMPILER_H

#define _ASM_COMPILER_H



/*

 * With GCC 4.5 onwards we can use __builtin_unreachable to indicate to the

 * compiler that a particular code path will never be hit. This allows it to be

 * optimised out of the generated binary.

 *

 * Unfortunately at least GCC 4.6.3 through 7.3.0 inclusive suffer from a bug

 * that can lead to instructions from beyond an unreachable statement being

 * incorrectly reordered into earlier delay slots if the unreachable statement

 * is the only content of a case in a switch statement. This can lead to

 * seemingly random behaviour, such as invalid memory accesses from incorrectly

 * reordered loads or stores. See this potential GCC fix for details:

 *

 *   https://gcc.gnu.org/ml/gcc-patches/2015-09/msg00360.html

 *

 * It is unclear whether GCC 8 onwards suffer from the same issue - nothing

 * relevant is mentioned in GCC 8 release notes and nothing obviously relevant

 * stands out in GCC commit logs, but these newer GCC versions generate very

 * different code for the testcase which doesn't exhibit the bug.

 *

 * GCC also handles stack allocation suboptimally when calling noreturn

 * functions or calling __builtin_unreachable():

 *

 *   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365

 *

 * We work around both of these issues by placing a volatile asm statement,

 * which GCC is prevented from reordering past, prior to __builtin_unreachable

 * calls.

 *

 * The .insn statement is required to ensure that any branches to the

 * statement, which sadly must be kept due to the asm statement, are known to

 * be branches to code and satisfy linker requirements for microMIPS kernels.

 */

#undef barrier_before_unreachable

#define barrier_before_unreachable() asm volatile(".insn")



#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)

#define GCC_IMM_ASM() "n"

#define GCC_REG_ACCUM "$0"

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